1. Field of the Invention
The present invention relates to ultrasonic dental scalers, and more particularly, relates to an ultrasonic dental scaler which is adapted to be either manually or automatically tuned to a resonant frequency of a scaler insert.
2. Description of the Prior Art
Ultrasonic dental scalers are commonly used in a variety of dental and periodontal procedures. Generally, in an ultrasonic dental scaler, vibrational motion of a transducer is transformed to flexural or elliptical motion of a dental scaler insert tip. Common frequencies of operation are 25 kHz and 30 kHz, although frequencies as low as 18 kHz and as high as 40 kHz have been used. In most cases, the scaler also includes a means for irrigating the area around the scaler tip by dispensing a liquid, such as water, through or over the surface of the scaler tip.
Ultrasonic dental scalers usually comprise a handpiece adapted for receiving a dental scaler insert which includes a scaling tool, a flexible cable connecting the handpiece to a housing and the dental scaler device electronics contained within the housing. There are several different types of ultrasonic dental scaler devices including magnetostrictive scaling inserts and piezoelectric scaling inserts.
Conventional ultrasonic magnetostrictive dental scalers generally include a dental handpiece having an ultrasonic transducer positioned within an energizing coil located within a sleeve. The transducer or scaler insert conventionally comprises a stack of laminar plates of magnetostictive material that is excited by the energizing coil to longitudinally expand and contract the transducer at an operational resonant frequency.
To properly vibrate the dental scaler insert, the electronic circuit for the scaler unit generally includes an oscillating circuit having a variable output amplitude. The frequency of the oscillator is adjusted to the mechanical resonant frequency of the scaler insert. Traditionally, this adjustment or tuning was achieved either by a manually tuned circuit adjusted by the operator for optimum vibration or, in the alternative, automatically using a feedback coil in the handpiece coupled to associated control circuitry to electronically adjust the variable frequency oscillator to the correct output frequency.
The feedback coil is generally formed by winding a wire near the base of the handpiece. The feedback coil is provided to register a voltage developed by the movement of the ultrasonic scaler insert within the electromagnetic field of the handpiece. Associated control circuitry uses this information to electronically adjust the variable frequency oscillator to the correct output frequency.
A disadvantage of the ultrasonic dental scaler devices described above is that the dentist must choose between a scaler device which is either manually tuned or one which is automatically tuned. However, several new periodontal techniques are more easily performed using a manually tuned scaler, while general removal of calculus and other dental techniques are more easily performed using an automatically tuned dental scaler device. Accordingly, in order for the dentist to have the flexibility to perform all the currently utilized dental and periodontal techniques, the dentist would be required to have two ultrasonic dental scalers, namely, a manually tuned unit for those procedures in which manual tuning is preferred and an automatically tuned unit for those procedures in which it is preferred to automatically tune to the resonant frequency of the scaler insert. Thus, it would be advantageous to provide dentists with a choice of a dental scaler unit which can be selectively switched between a manually tuned circuit and an automatically tuned circuit depending upon the procedure being performed by the dentist.
Several periodontal techniques currently being used also require the ability of the dentist to offset slightly the oscillation frequency which has been automatically tuned by a tuning circuit. Conventional automatically tuned dental scalers do not provide dentists with the capability to manually offset the automatically tuned oscillation frequency. Thus, it would be advantageous to include a control means so that the oscillation frequency could be offset slightly either above or below the automatically tuned center frequency provided by the tuning circuit.
Thus, the present invention is directed toward overcoming the disadvantages of conventional dental scalers which have been discussed above.